Light guide, illuminating device having the light guide, and image reading device and information processing apparatus having the illuminating device

ABSTRACT

In an illumination device, a light guide is adapted to emit the light from a face thereof and is provided with an area, on a face opposite to the light emitting face, for diffusing and/or reflecting the light introduced into the light guide from an end face thereof or is provided with uneven light emitting characteristics along the longitudinal direction of the light guide, and the center of the light source positioned at the end of the light guide is placed at a position aberrated from the normal line to the area, whereby attained are compactness, a low cost, a low electric power consumption, a high efficiency of utilization of the light emitted by the light source, and excellent and uniform illumination characteristics. An image reading device and an information processing apparatus can also be equipped with the above-mentioned illumination device.

This application is a divisional application of application Ser. No.11/336,982, filed Jan. 23, 2006, which is a divisional application ofapplication Ser. No. 10/295,925, filed Nov. 18, 2002, now U.S. Pat. No.7,057,778, which is a continuation of application Ser. No. 08/948,661,filed Oct. 10, 1997, now U.S. Pat. No. 6,512,600, which is a divisionalapplication of application Ser. No. 08/471,756, filed Jun. 6, 1995, nowabandoned, which is a divisional application of application Ser. No.08/183,367, filed Jan. 19, 1994, now U.S. Pat. No. 5,499,112, the entirecontents of all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light guide, an illuminating devicehaving the light guide, and an image reading device and an informationprocessing apparatus having the illuminating device, and moreparticularly an information processing apparatus (such as a copyingmachine, a facsimile apparatus, a scanner or an electronic blackboard),an image reading device adapted for use in such an informationprocessing apparatus, an illumination device adapted for use in such animage reading device, and a light guide adapted for use in such anillumination device.

2. Description of the Related Art

For illuminating the image reading device of the information processingapparatus such as the facsimile apparatus, electronic copying machine orthe like, there has conventionally been employed a discharge tube suchas a florescent lamp or an LED array consisting of an array of aplurality of LED's. Particularly in recent years, the LED arrays arebeing used more widely, because compact and inexpensive products arerequested for home-use equipment such as the facsimile apparatus.

An example of the illumination device utilizing such LED array will beexplained with reference to FIGS. 1A and 1B, wherein shown are an LEDarray 41, a plane 42 to be illuminated, such as the surface of anoriginal document, and LED chips 43. FIG. 1A shows the schematicstructure of the illumination device employing an LED array, togetherwith the original to be illuminated, while FIG. 1B shows an example ofthe illumination intensity distribution of the surface of the originalwhen it is illuminated with the illumination device shown in FIG. 1A. Asshown in FIG. 1B, a substantially uniform and high illuminationintensity can be obtained by increasing the number of the LED chips,namely by densely arranging the LED chips. However, because of theincreased number of the LED chips, it is difficult to achieve asufficiently low cost, and to reduce the power consumption beyond acertain limit even though the power required for an individual LED isquite low.

A reduced number of the LED chips, or a less dense arrangement of theLED chips, for the purpose of cost reduction, will result in an unevenillumination intensity distribution on the illuminated surface, due tothe increased gap between the LED chips, as will be explained in thefollowing with reference to FIGS. 2A and 2B, wherein the same componentsas those in FIGS. 1A and 1B are represented by the same numbers.

FIG. 2A shows the schematic structure of the illumination deviceutilizing an LED array, together with the illuminated original, as inFIG. 1A, while FIG. 2B shows an example of the illumination intensitydistribution when the original is illuminated with the illuminationdevice shown in FIG. 2A. If the number of LED's in the array isdecreased, there results, as shown in FIG. 2B, an extremely unevenillumination state in which the illumination intensity on the originalsurface is high in positions corresponding to the LED chips but is lowin positions corresponding to the gaps between the LED chips. Theprecise original reading becomes difficult under such an illuminationintensity distribution, and a circuit is required to compensate for theunevenness in the illumination intensity distribution, eventuallyleading to a higher cost.

FIG. 3 is a schematic perspective view showing the details of a linearlight source similar to that explained above.

As shown in FIG. 3, such a linear light source is composed of LED chips43, individually constituting a point light source, mounted linearly ona substrate 45 bearing electric wirings 49, and a voltage is appliedbetween input terminals 48 of the wirings 49 to cause light emissionfrom the LED chips 43, thereby constituting a linear light source.

FIG. 4 shows an elevation view of the light source, seen from adirection C shown in FIG. 3, and the light amount distribution on anilluminated surface (not shown), schematically illustrating thevariation of the light amount corresponding to the positions of the LEDchips 43. A curve 44 indicating the distribution of the light amountbecomes higher in positions directly above the LED chips 43 but lower inpositions corresponding to the gaps between the LED chips 43, because ofthe linear arrangement thereof. As a result, there is formed unevennessin the light amount corresponding to the arrangement of the LED chips43. In reading image information with such a linear light source, thereflected light from the illuminated surface also involves unevenness inthe light amount similar to that shown in FIG. 4, so that a large burdenis required in the post-process such as image processing for improvingthe tonal rendition.

On the other hand, there is conceived a linear light source of theconfiguration as shown in FIG. 5, in which a light bulb, such as atungsten lamp or a halogen lamp, is employed as the light source and thelight emitted from the light source is developed into a linear form. InFIG. 5 there are shown an electric light bulb 1, such as a halogen lamp;a mirror 2 of a light condensing form, such as spherical or ellipticalform; a translucent member 3 with a circular cross section, such as aquartz rod; an entrance face 4 where the light beam emitted from thelight bulb 1 enters the translucent member 3; an area 5 for taking outthe light beam, propagating in the translucent member 3, from the memberby reflection or scattering, the area 5 being formed on a part of thetranslucent member 3 by forming a coarse surface or coating the surfacethereof with light diffusing/reflecting paint; and a reflective face 6provided at an end of the translucent member 3 opposite to the bulb 1and formed either by evaporating a metal such as aluminum or applyinglight diffusing/reflecting paint on the end face of the translucentmember 3 itself, or as a separate member. The translucent member 3 mayalso have a square or rectangular cross section.

The light beam L, emitted from the light bulb 1 and entering thetranslucent member 3 through the entrance face 4 thereof propagates inthe member 3 by repeated reflections on the internal walls thereof, thenis reflected by the end face opposite to the entrance face 4, andpropagates again in the interior of the translucent member 3. In thecourse of repeated reflections, upon entering the above-mentioned area5, the light beam is scattered therein and a part 1 ₁ of the light beamis released to the exterior through an exit face opposite to the area 5.The remaining part 1 ₂ of the diffused light beam, entering the exitface diagonally, is totally reflected thereon and propagates in thetranslucent member. The light reaching the entrance face 4 afterrepeated propagations is released therethrough to the exterior.

When the light bulb 1 is used as the light source, as the amount oflight emission can be increased by the use of a larger electric power,there can be obtained a considerably high illumination intensity despitethe light loss by the light emission to the exterior through theentrance face 4.

However, the use of the light bulb is associated with the drawbacks of alarge electric power consumption in return for a high illuminationintensity, difficulty in compactization of the device because of thelarge heat generation, and lack of maintenance-free character as in thecase of LED's, since the electric light bulb has a service lifeconsiderably shorter than even that of the fluorescent lamp and has tobe replaced when the light amount becomes low or when the filament isbroken.

Consequently, the illumination device to be employed as the imagereading light source for an information processing apparatus, such as afacsimile apparatus, preferably employs LED's as the light source and isadapted to emit the light beam from the LED's in a linear form. Asanother example of the illumination device employing the LED chips asthe light source, there has been conceived a configuration shown inFIGS. 6A and 6B, which respectively are a schematic view of theillumination device together with an original to be illuminated, and achart showing an example of the illumination intensity distribution onthe illuminated surface 42 when the original is illuminated with thedevice shown in FIG. 6A. More specifically, the illumination deviceshown in FIG. 6A is similar to that shown in FIG. 5 except that thelight source is replaced by an LED light source 71. In FIG. 6A, thecomponents equivalent to those in FIG. 5 are represented by the samenumbers.

The LED light source is available in various types, among which there isknown so-called surface mounting LED chips convenient for compactizationand actual mounting. FIG. 7 illustrates such a surface mounting LEDlight source, wherein shown are an LED chip 81; a substrate 82; areflecting frame 83; translucent resin 84; and electrodes 85, 86 formedon the substrate 82. Such an LED light source is already available in acompact form, with the size of the light source itself of 2-3 mm and theheight of 2 mm or less. As the electrodes 85, 86 are extended to therear side of the substrate 82 through the lateral faces thereof, thelight source can be efficiently mounted on the mounting substrate,merely by placing on the mounting substrate printed with cream solderand heating in a reflow oven. Consequently, the use of such an LED lightsource is more desirable for constructing a linear light source.

However, since such an LED light source has a directionality in thelight emission as shown in FIG. 7, in illuminating the original incombination with the translucent member 3 as shown in FIG. 6A, anunevenness will result in the illumination intensity distribution, whichis higher at the side of the LED light source 71 and is lower in theremaining part, as shown in FIG. 6B.

This is because the lights diagonally emitted from the LED light source71 directly enter the area 5 of the translucent member 3, are scatteredin the area 5 and released from the translucent member 3.

FIG. 8 is a schematic perspective view of another example of theconventional linear light source, in which light sources are provided onboth ends of an oblong translucent member constituting a light guide 3.In FIG. 8, the light is emitted in a direction 1 ₁. The oblongtranslucent member 3 has a constant cross section, and the faces thereofare formed as mirrors except for the light-emitting face. The light isintroduced from LED chips 71 provided on substrates 45 into the oblongtranslucent member 3 through the end faces thereof, and is released tothe exterior either directly or after reflection by the mirror faces ofthe translucent member 3. FIG. 9 shows an elevation view, seen from adirection D shown in FIG. 8, and the illumination intensity distributionon the illuminated surface (not shown). As shown in FIG. 9, there isobtained a uniform light amount within an area a-c, but the level oflight amount is low and is considerably different from that in thevicinity of the light source. 10 a, 10 b and 10 c are cross sections atthe positions a, b and c of the oblong translucent member 3, and 44 a,44 b and 44 c indicate the illumination intensity distributions at thecorresponding positions. Also hatched portions represent mirror faces(except for the light emitting face and light entering faces of theoblong translucent member 3).

SUMMARY OF THE INVENTION

An object of the present invention is to resolve the drawbacksassociated with the conventional illumination means utilizing the lineararray of LED chips and with the information processing apparatusemploying such an illumination means, such as the difficulty inachieving a sufficiently low cost due to the large number of LED chipsto be used, the limit in reducing the electric power consumption eventhough the electric power consumption in an individual LED chip isrelatively low, the uneven illumination state where the illuminationintensity on the illuminated original is high in positions correspondingto the LED chips but is low in positions corresponding to the gapsbetween the LED chips, encountered when the number of the LED chips isreduced in the array, the uneven illumination intensity on theilluminated original encountered when the LED chips are positioned atthe end faces of the translucent member, and the cost increase resultingfrom the necessity for a circuit to compensate for the unevenness in theillumination intensity.

Another object of the present invention is to resolve the drawbacksassociated with the conventional illumination means utilizing theelectric light bulb and with the information processing apparatusemploying such an illumination means, such as the large electric powerconsumption, the difficulty in compactization of the device because ofthe large heat generation, and the difficulty in attaining amaintenance-free configuration.

Still another object of the present invention is to provide anillumination device with high uniformity in the illumination intensity,a low electric power consumption and easy compactization, a light guideadapted for use in the illumination device, and an informationprocessing apparatus utilizing the illumination device.

Still another object of the present invention is to resolve thedrawbacks of the unevenness in the illumination intensity and of thesignificant difference in the illumination intensity between a sideclose to the LED light source and the opposite side, when the LED isemployed as the light source for a linear illumination device.

Still another object of the present invention is to provide a lightguide having a light entrance face at an end thereof and a light exitface for emitting the introduced light, along the longitudinaldirection, different from the end face, comprising an area providedalong the longitudinal direction in a part of the side opposite to thelight exit face and adapted to reflect and/or diffuse the light beamintroduced into the translucent member.

Still another object of the present invention is to provide anillumination device provided with a translucent member having a lightentrance face at an end thereof and a light exit face for emitting theintroduced light on a face, along the longitudinal direction, differentfrom the end face, and a light source for emitting the light beam to beintroduced through the light entrance face, wherein the translucentmember comprises an area provided along the longitudinal direction on apart of the side opposite to the light exit face and adapted to reflectand/or diffuse the light introduced into the translucent member, and thecenter of the light source is aberrated from the direction of a normalline to the area.

Still another object of the present invention is to provide aninformation processing apparatus provided with:

(a) a photoelectric converting device having a plurality ofphotoelectric converting elements positioned opposite to the image of anoriginal sheet to be read;

(b) an illumination device for illuminating the original sheet;

(c) transport means for transporting the original sheet;

(d) an output unit for recording an image on a sheet by electricalsignals corresponding to image information; and

(e) a controller for controlling the photoelectric converting device,the light source, the transport means and the output unit;

wherein the illumination means includes an illumination device providedwith a translucent member having a light entrance face at an end thereofand a light exit face for emitting the introduced light, along thelongitudinal direction, different from the end face, and a light sourcefor emitting the light beam to be introduced through the light entranceface, wherein the translucent member comprises an area provided alongthe longitudinal direction on a part of the side opposite to the lightexit face and adapted to reflect and/or diffuse the light introducedinto the translucent member, and the center of the light source isaberrated from the direction of a normal line to the area.

Still another object of the present invention is to provide an imagereading device including an illumination device provided with atranslucent member having a light entrance face at an end thereof and alight exit face for emitting the introduced light, along thelongitudinal direction, different from the end face, and a light sourcefor emitting the light beam to be introduced through the light entranceface, and also including a photoelectric converting device for receivingthe light emitting from the light exit face and reflected by anilluminated area, wherein the translucent member comprises an areaprovided along the longitudinal direction on a part of the side oppositeto the light exit face and adapted to reflect and/or diffuse the lightintroduced into the translucent member, and the center of the lightsource is aberrated from the direction of a normal line to the area.

Still another object of the present invention is to provide a lightguide for use in an illumination device, composed of a translucentmember adapted to receive the light from a light source through a faceof the translucent member and to emit the light through a lateral facethereof, wherein the translucent member has uneven light emissioncharacteristics in the longitudinal direction thereof.

Still another object of the present invention is to provide anillumination device including a light source positioned on a face of atranslucent member and adapted to emit the light from a lateral face ofthe translucent member, wherein the translucent member has uneven lightemission characteristics along the longitudinal direction thereof.

Still another object of the present invention is to provide an imagereading device provided with an illumination device including a lightsource positioned on a face of a translucent member and adapted to emitthe light from a lateral face of the translucent member, and aphotoelectric converting device adapted to receive the light emitted bythe illumination device and reflected by an illuminated area, whereinthe translucent member has uneven light emission characteristics alongthe longitudinal direction thereof.

Still another object of the present invention is to provide aninformation processing apparatus provided with:

(a) a photoelectric converting device including a plurality ofphotoelectric converting elements positioned opposite to the image of anoriginal sheet to be read;

(b) an illumination device for illuminating the original sheet, thedevice including a light source positioned on a face of a translucentmember and adapted to emit the light from a lateral face thereof;

(c) transport means for transporting the original sheet;

(d) an output unit for recording an image on a sheet by electricalsignals corresponding to the image information; and

(e) a controller for controlling the photoelectric converting device,the light source, the transport means and the output unit;

wherein the translucent member of the illumination means has unevenlight emission characteristics along the longitudinal direction thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, 2A, 2B, 3 and 4 are views showing examples of theillumination device utilizing an LED array;

FIGS. 5, 6A and 6B are views showing examples of the illumination deviceutilizing a translucent member;

FIG. 7 is a schematic cross-sectional view showing an example of the LEDlight source;

FIG. 8 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIG. 9 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIG. 10 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIG. 11 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIG. 12 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIG. 13 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIG. 14 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIG. 15 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIG. 16 is a view showing preferred embodiment of the light guide andthe illumination device of the present invention;

FIGS. 17A to 17C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIG. 18 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIGS. 19A to 19C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 20A to 20C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 21A to 21C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 22A to 22C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 23A and 23B are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 24A to 24C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 25A to 25C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 26A to 26C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIG. 27 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIG. 28 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIGS. 29A to 29C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 30A to 30C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 31A to 31C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIG. 32 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIG. 33 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIGS. 34A to 34C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 35A to 35C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 36A and 36B are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 37A to 37C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 38A to 38C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 39A to 39C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIG. 40 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIG. 41 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIGS. 42A to 42C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 43A to 43C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 44A and 44B are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 45A to 45C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 46A to 46C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 47A to 47C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 48A and 48B are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIG. 49 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIGS. 50A to 50C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 51A to 51C are views showing preferred embodiments of the lightguide and the illumination device of the present invention;

FIGS. 52 and 53 are schematic cross-sectional views showing preferredmounting methods of the light source;

FIG. 54 is a view showing preferred embodiments of the light guide andthe illumination device of the present invention;

FIG. 55 is a schematic cross-sectional view of an information processingapparatus in which the illumination device of the present invention isapplicable;

FIGS. 56 to 58 are schematic partial cross-sectional views showinginformation processing apparatus employing the illumination device ofthe present invention;

FIG. 59 is a schematic perspective view of an ink jet recording headapplicable to the information processing apparatus of the presentinvention;

FIGS. 60 and 62 are schematic perspective views showing examples of theink jet recording unit applicable to the information processingapparatus of the present invention; and

FIG. 61 is a block diagram showing an example of the configuration ofthe information processing apparatus of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the illumination device consisting of the aforementioned linear lightsource, the total light amount is low and the light intensitydistribution is uneven as explained before. This is because the lightfrom the light source consisting of the LED chip is not emitted, in auniform and sufficient manner, from the oblong translucent member (lightguide) 3 to the exterior.

According to the present invention, the oblong translucent member (lightguide) is given uneven light emission characteristics along thelongitudinal direction thereof, thereby attaining almost uniform lightemission characteristics along the longitudinal direction over theentire linear light source. Thus the difference in the light amountbetween an area close to the light source and an area far from the lightsource can be reduced, and there can thus be realized a linear lightsource showing reduced unevenness in the light amount on the illuminatedsurface.

Also there can be realized an illumination device with reducedunevenness in the light amount, by providing the translucent member withan area for reflecting and/or diffusing the light introduced into themember and specifying the position of the area.

Now the present invention will be clarified in detail by preferredembodiments thereof, shown in the attached drawings.

Embodiment 1

FIG. 10 is a perspective view showing an embodiment 1 of the linearlight source of the present invention, wherein shown are an oblongtransparent (translucent) member 3, substrates 45; LED chips 71 mountedon the substrates 45, and a light emitting direction 1 ₁. A lateral face3 a of the transparent member 3 constitutes the light emitting face,while other lateral faces 3 b, 3 c and 3 d are formed as mirror faces toconstitute light reflecting faces.

The oblong transparent member 3 is provided at both ends thereof withthe LED chips 71 constituting the light sources, and the light therefromenters the transparent member 3 from the end faces thereof and isemitted from the lateral face 3 a in the direction 1 ₁ either directlyor after reflection on the lateral faces 3 b, 3 c, 3 d. In thisembodiment, the lateral face 3 d is tapered so that the transparentmember 3 has a smaller cross section at the center, whereby the lightcan be efficiently reflected in the direction 1 ₁. In this embodiment,the lateral face 3 d is inclined by a constant angle, but such aconstant angle is not essential.

FIG. 11 shows the elevation view of the light source seen from adirection A in FIG. 10 and the light intensity distribution on anilluminated surface (not shown), wherein a curve 44 shows theillumination intensity distribution, while 10 a, 10 b, 10 c show thecross sections of the transparent member 3 at positions a, b, c, and 44a, 44 b, 44 c indicate the illumination intensity distributions at thepositions. The present embodiment can provide a uniform light amountdistribution with an increased amount of light in the area a-c.

Embodiment 2

FIG. 12 shows the elevation view of an embodiment 2 of the linear lightsource of the present invention, seen from the direction A shown in FIG.10, and the light amount distribution on an illuminated surface (notshown). Components that are the same as those shown in FIGS. 10 and 11are represented by the same numbers and will not be explained further.

In the present embodiment, the lateral face 3 d of the oblongtransparent member 3 is tapered so as to reduce the cross sectionthereof at the center as in Embodiment 1, and the transparent member 3is formed so as to have a trapezoidal cross section having the shorterside at the light emitting face and the longer side at the oppositeface. Such a trapezoidal cross section, as shown in FIG. 12, allows thelight to be emitted in the transparent member 3, in a more condensedstate, into the direction 1 ₁, thereby increasing the illuminationintensity on the illuminated surface, in comparison with Embodiment 1,within the area a-c. The cross section of the oblong transparent member3 is not limited to the trapezoidal form but may also be formed as apartially cut-off circle, as shown in FIG. 13.

Embodiment 3

FIG. 14 is a plan view of an embodiment 3 of the linear light source ofthe present invention, seen from a direction B shown in FIG. 10, andFIG. 16 shows the elevation view of the embodiment seen from a directionB shown in FIG. 10 and the light amount distribution. Components thatare the same as those shown in FIGS. 10 and 11 are represented by thesame numbers and will not be explained further.

As shown in FIG. 14, the oblong transparent member 3 of this embodimentis provided, in the vicinities of the light sources on the lightemitting lateral face 3 a, with light attenuating films 306, whichattenuate the light emitted from the vicinity of the light sources,thereby providing a light amount distribution, as shown in FIG. 16, onthe illuminated surface.

The attenuating films 306 may be replaced by light shielding films 307for reducing the light amount in the vicinity of the light source. FIG.15 is a plan view showing an example in which the light shielding filmsare provided in the vicinities of the light sources, on the lightemitting lateral face 3 a of the oblong transparent member 3. The lightamount distribution, as shown in FIG. 16, may also be obtained on theilluminated surface by intercepting the light in the vicinity of thelight source by means of the light shielding films 307 as shown in FIG.15.

Embodiment 4

FIGS. 17A to 17C are schematic views of an embodiment 4 of theillumination device of the present invention, wherein FIG. 17A is aschematic lateral view of the device, illustrated together with anoriginal constituting the illuminated surface, FIG. 17B is a schematiccross-sectional view of the translucent member 3 and an area 5, cut in aplane perpendicular to the plane of FIG. 17A, and FIG. 17C is aschematic lateral view of the device, seen from a direction A shown inFIG. 17A. As shown in these drawings, the illumination device of thisembodiment is provided with an LED light source 8 at an end face in thelongitudinal direction of a translucent member 3 of a rectangular crosssection, and with an area 5 for reflecting (or diffusing) the lightbeam, provided in a part of the translucent member 3 on a face opposedto the light emitting area thereof and formed by a coarse surface or bya coating with light diffusing-reflecting paint. On the end faceopposite to the LED light source 8, there is formed a reflecting portion6 adapted to reflect the light propagating in the translucent member 3and formed by evaporation of a metal such as aluminum or by coating oflight diffusing-reflecting paint on the end face itself of thetranslucent member 3 or by forming such means as a separate member.

In this embodiment, as shown in FIG. 17C, the center of the LED lightsource is aberrated (with an offset) from the normal line passingthrough the center of the shorter width of the area 5.

The light beam emitted from the LED light source 8 normally propagatesinside the translucent member by repeated reflections therein, andreturns toward the LED light source 8 after reaching the reflectingportion 6. Also, the light entering the area 5 in the course ofpropagation is diffused or reflected therein and emitted through theexit portion toward the original constituting the illuminated surface (1₁) or propagates again within the translucent member by reflectionstherein (1 ₂).

In this embodiment, since the LED light source 8 is aberrated from thenormal line passing through the center of the width of the area 5, thelight directly entering the area 5 from the LED light source 8 isreduced, so that there can be sufficiently resolved the unevenness thatthe illumination intensity is higher only at the side of the LED lightsource 8 in the longitudinal direction of the translucent member 3. Alsosince the light entering the area 5 is principally the indirect lightreflected inside the translucent member 3 after being emitted from theLED light source 8, the light beam emitted from the exit portion is madeuniform over the longitudinal direction of the translucent member 3.

These situations will be explained further in the following, withreference to the attached drawings.

FIG. 18 shows a lateral face that is the same as that shown in FIG. 17C,wherein a part of the light emitted from the LED light source 8 isindicated by arrows 1 ₃, 1 ₄, which respectively indicate direct andindirect lights from the light source 8.

In the present embodiment, since the LED light source 8 is aberratedfrom the normal line passing through the center of the area 5, theproportion of the direct light 1 ₃ decreases while that of the indirectlight 1 ₄ increases, so that the light beam emitted from the exitportion can be made uniform over the entire translucent member 3.

The amount of the aberration of the LED light source 8 is defined as atleast out of the normal line passing through the center of the area 5,but it should be suitably determined in practice, because in case of anexcessively large amount of aberration, the light coming from the LEDlight source 8 is mostly composed of the indirect light and there willalso result in a loss of the light beam in the translucent member 3. Inparticular, an extremely large aberration should he avoided since theillumination intensity becomes lower at the side of the LED light source8.

FIGS. 19A to 19C are given for explaining the difference between theillumination device of the present embodiment and other illuminationdevices. In these drawings there are shown schematic lateral views ofthe translucent member and the LED light source, seen from a directionsimilar to the direction A in FIG. 17A and corresponding illuminationintensity distributions along the longitudinal direction of thetranslucent member. FIGS. 19A and 19B illustrate reference examples tobe compared with the device of the present embodiment, while FIG. 19Cillustrates the device of the present embodiment.

FIG. 19A shows an example employing a translucent member of circularcross section, which is positioned so that the center thereof coincideswith the center of the LED light source and the center lies on thenormal line passing through the center of the area 5. Also FIG. 19Bshows an example employing a translucent member of rectangular crosssection, which is positioned so that the crossing point of the diagonalsof the rectangular cross section coincides with the center of the LEDlight source and the center lies on the normal line passing through thecenter of the area 5.

On the other hand FIG. 19C shows an example of the illumination deviceof the present embodiment, employing a translucent member of rectangularcross section, wherein the center of the LED light source 8 is aberratedby a distance “a” from the normal line passing through the center of thewidth of the area 5.

In all the cases, the center of the light source is separated by a samedistance “a” from a face of the translucent member on which the area 5is formed.

The light emitted from the LED light source 8 and introduced into thetranslucent member can be divided into direct incident light enteringthe area 5 directly without any reflection on the internal walls of thetranslucent member, and indirect incident light entering the area 5after at least a reflection on the internal walls of the translucentmember.

The amount of the direct incident light depends on the angle Δθ of thearea 5 seen from the LED light source 8, and increases with an increasein the angle. In the arrangements shown in FIGS. 19A and 19B, where theLED light source is positioned directly above the area 5, the angle canbe represented as Δθ={2tan⁻¹(w/2)/2}≅w/a, wherein “w” is the width ofthe area 5 and “a” is the distance along the normal line from the LEDlight source to the light exit face.

On the other hand, in the present embodiment shown in FIG. 19C, whereinthe LED light source is not positioned directly above the area 5 but isaberrated laterally by a distance “a”, the angle can be represented asΔθ=2tan⁻¹{(w/2×2^(1/2))/2^(1/2)×a }≅w/2a, and is therefore about a halfof the angle that is depicted in the arrangements shown in FIGS. 19A and19B.

For this reason, the amount of the direct incident light becomes lowerin the present embodiment than in the conventional configurations. Onthe other hand, the amount of indirect incident light increasescorrespondingly. As a result, the entire illumination intensitydistribution is improved, because of the relaxation of the peak in thevicinity of the LED light source.

These situations will be readily understood from the curves of therelative illumination intensity as a function of the distance from thelight source. In the case of FIGS. 19A and 19B, the direct incidentlight has a peak and shows a high light amount at the side of the lightsource, so that the total light amount, consisting of the direct andindirect incident lights, is uneven, having a peak at the side of thelight source. On the other hand, the present embodiment shown in FIG.19C provides a uniform light amount over the entire device, though thelight amount at the light source side is lowered. Consequently, theillumination device of the present embodiment is more convenient foruse.

Embodiment 5

FIGS. 20A to 20C show a variation of the illumination device of thepresent invention shown in FIGS. 17A to 17C. The variation is differentfrom the latter in that the translucent member 3 is provided with aprotruding portion 35, and the area 5 is formed on an end face of theprotruding portion 35, in order to further reduce the direct incidentlight from the LED light source.

As the area 5 is formed on the lower face of the protruding portion 35,extended from a face 31 of the translucent member 3, as shown in FIGS.19A to 19C, the amount of direct incident light from the LED lightsource to the area 5 becomes smaller in comparison with the case shownin FIGS. 17A to 17C. Stated differently, most of the light emitted fromthe LED light source does not enter the area 5 directly but after atleast a reflection within the translucent member 3.

Thus, in the illumination device shown in FIGS. 20A to 20C, the amountof direct incident light decreases and the proportion of the indirectincident light becomes even higher. In comparison with the case shown inFIG. 19C, the illumination intensity at the light source side is lowerdue to the decreased proportion of the direct incident light, and theillumination intensity of the indirect incident light increases, thoughslightly, due to the increased proportion of the indirect incidentlight.

Consequently, in the configuration shown in FIGS. 20A to 20C, providingthe translucent member 3 with a protruding portion and forming the area5 on the end face thereof allows obtaining a higher illuminationintensity with improved uniformity.

Embodiment 6

FIGS. 21A to 21C show another variation of the device shown in FIGS. 17Ato 17C. In this variation, the translucent member 3 is extended to aside opposite to the LED light source, with respect to the area 5.

Such a configuration achieves more uniform illumination intensity forthe indirect incident light, so that, though the illumination intensityis higher at the light source side, the illumination intensity becomesmore uniform in the remaining portion excluding a part at the lightsource side.

Embodiment 7

FIGS. 22A to 22C show an illumination device in which the configurationsshown in FIGS. 20A to 20C and FIGS. 21A to 21C are combined. Morespecifically, the translucent member is provided, on a face opposite tothe light exit face, with a protruding portion 35, and the area 5 isformed on the end face of the protruding portion 35, and the translucentmember 3 is extended to a side opposite to the light source 8 withrespect to the area 5.

In such a combined structure, the area 5 principally receives theindirect incident light more reflected within the translucent member 3,so that the illumination intensity distribution becomes more uniform forthe indirect incident light. The situation for the direct incident lightis similar to the configuration shown in FIGS. 20A to 20C.

Consequently, the total illumination intensity becomes more uniform incomparison with the case shown in FIGS. 20A to 20C, since thecontribution of the indirect incident light is made more uniform.

Embodiment 8

The light amount of the LED light source is less than that of theincandescent electric bulb. For increasing the light amount, the numberof the LED chips can be increased.

For positioning a larger number of the LED light sources whilesatisfying the principle of the present invention, the end face of thetranslucent member, where the LED light sources are to be positioned,can be made larger.

For example, as shown in FIG. 23A, an increase in the light amount canbe achieved by positioning an LED light source 8 also on the extendedside of the translucent member 3. In such a case, both the direct andindirect incident lights to the area 5 increase, but the illuminationintensity can be made more uniform over the entire area, without localincrease at the side of the LED light source 8, by suitably balancingthe amounts of the direct and indirect incident lights from the LEDlight source 8 to the area 5 (for example, by suitably separating theposition of the LED light source 8 from the protruding portion 35 (area5)).

On the other hand, if the LED light sources 8 on both sides of the area5 (protruding portion 35) are separated from the area 5, theillumination intensity may decrease at the side of the LED light sources8 due to the decrease of the direct incident light into the area 5 andmay increase at the side far from the LED light sources 8 due to theincreased proportion of the indirect incident light into the area 5. Insuch a case, there may be provided an additional LED light source 8, asshown in FIG. 23B, in a position corresponding to the area 5 (protrudingportion 35) of the translucent member. Such an arrangement increases theillumination intensity both at the side of the LED light sources 8 andat the side far therefrom. Naturally, such an arrangement of the LEDlight sources 8 is to be designed in consideration of the balance of thedirect and indirect incident lights into the area 5.

Since the illumination intensity of the illumination device isapproximately proportional to the number of the LED chips, theconfiguration as shown in FIG. 23A or 23B enables an additional increasein the illumination intensity.

The arrangement of the LED light sources as shown in FIG. 23A or 23B,which has little effect on the size of the illumination device incomparison with those shown in FIGS. 21A to 21C and 22A to 22C, isdesirable in case a higher illumination intensity is required.

Embodiment 9

For achieving a more uniform and higher illumination intensity, it isdesirable, instead of providing the LED light source 8 only at an endface of the translucent member 3 as in the foregoing embodiments, toprovide the LED light sources 8 on both end faces of the translucentmember 3.

An example of such an arrangement is shown in FIGS. 24A to 24C, whereinFIG. 24A is a schematic lateral view of the illumination device of thepresent embodiment, illustrated together with an original constitutingthe illuminated surface, while FIG. 24B is a schematic cross-sectionalview of the translucent member 3 and the area 5 along a planeperpendicular to the plane of FIG. 24A, and FIG. 24C is a schematiclateral view of the illumination device seen from a direction A shown inFIG. 24A.

As shown in these drawings, the illumination device of the presentembodiment is provided with the LED light sources 8 on both end faces ofthe translucent member 3, so that the illumination intensity can beincreased further and the distribution of the illumination intensity canbe made symmetrical along the longitudinal direction of the translucentmember 3. Also in the foregoing embodiments 4 to 8, there may naturallybe provided the LED light sources 8 on both end faces of the translucentmember 3. Such LED light sources 8 are preferably provided in the samenumber and arranged in a similar manner on both end faces, but suchconditions are not essential.

Embodiment 10

In an information processing apparatus, such as a facsimile apparatus,the area read by the line sensor in a scanning period, in a directionperpendicular to the scanning direction, namely in the direction ofrelative movement between the original and the sensor, is not so large.Also, among the light scattered and/or reflected in the area 5, only aportion emitted from the exit portion opposite to the illuminatedsurface contributes to the illumination thereof, as illustrated in FIG.41, and, since the admitted light is diffuse, the illumination intensityon the illuminated surface declines rapidly with an increase in distancefrom the light exit portion of the translucent member 3 to theilluminated surface.

Therefore, if a higher illumination intensity is desired, it iseffective to condense the light, emitted from the translucent member 3,by means of a lens.

FIGS. 25A to 25C show an example of such an arrangement, in which acylindrical lens 9 is provided, facing the illuminated surface and alongthe translucent member 3 of the illumination device shown in FIGS. 24Ato 24C. As shown in FIGS. 25A to 25C, the cylindrical lens 9 iseffectively positioned so that the center thereof corresponds to thearea 5, but such positioning is not essential as long as the necessaryillumination intensity can be obtained.

Such a lens arrangement, being capable of illumination of theilluminated surface by condensation of the light emitted from thetranslucent member 3, allows increasing the average illuminationintensity, though the distribution thereof is substantially notaffected.

Such an arrangement enables the use of a sensor of a lower sensitivity,or image reading with higher speed if the sensitivity of the sensor isnot changed. It can also resolve the loss in the light amount resultingfrom the color filters used in color image reading, while maintaining asufficiently high image reading speed.

Embodiment 11

The above-explained area 5, formed by a coarse surface or by coatingwith the light diffusing paint can uniformly diffuse the incident light,but it is not satisfactory in terms of the efficiency of utilization ofthe light emitted from the LED light source 8, since a proportion of thelight returns to the end face of the translucent member 3. To furtherincrease the average illumination intensity, therefore, theabove-mentioned area 5 may be replaced by a reflecting face of sawtoothshape.

FIGS. 26A to 26C show an embodiment in which the area 5 of theillumination device, shown in FIGS. 17A to 17C, is formed as areflecting face of sawtooth shape. The sawtooth-shaped reflecting faceof the area 5 can be formed, in a part of the lateral face of thetranslucent member 3, by integral molding with the translucent member 3,or by cutting work thereon, or by adhesion of a separate sawtooth-shapedmember onto the lateral face of the translucent member 3 with adhesivematerial or by ultrasonic adhesion. Among these, the integral moldingwith the translucent member 3 is preferable in consideration of the costand the decrease of the manufacturing steps. The surface of the area 5constituting the sawtooth-shaped reflecting face is preferably subjectedto the evaporation of a bright metal such as aluminum or silver.

As shown in FIG. 26A, a part of the light emitted from the LEDlight-source 8 enters the area 5, is reflected by the reflecting face ofthe area 5 and illuminates the illuminated surface. Since the area 5 inthis case is not composed of a coarse surface or a coating of the lightdiffusing paint, the light entering the area 5 is substantially notsubjected to diffuse reflection. Consequently, the incident light isefficiently reflected toward the illuminated surface.

Now reference is made to FIGS. 27 and 28 for further explaining thesawtooth-shaped reflecting face constituting the area 5.

FIG. 27 is a schematic cross-sectional view of the translucent member 3,and FIG. 28 is a partial magnified view of FIG. 27. The light L emittedfrom the LED light source 8 enters the translucent member 3 through theentrance end face 4, and propagates in the translucent member 3,repeating reflections therein. A part of the light L reaches thesawtooth-shaped reflecting face 7 of the area 5 after being reflected inthe translucent member 3, then is reflected in the area 5 and emergesfrom the translucent member 3.

In this manner, the light from the LED light source 8 enters thereflecting faces 7, arranged along the X-direction, of the area 5, thenis reflected by the reflecting faces and is taken out to the exterior.

The angle θ of the incident light from the LED light source 8 to theX-axis in the translucent member satisfies a relation −θ_(c)<θ<θ_(c),wherein θ_(c) is the critical angle determined by the refractive indexesof the translucent member and of the external medium (normally air).

Also, when the light propagates by repeating total reflections on thelateral face of the translucent member, the angle θ of such propagatinglight satisfies a condition -(90-θ)<θ<(90-θ_(c)), because the light hasto have an angle exceeding the critical angle θ_(c) with respect to thenormal line to the lateral face.

Consequently, in order that the light beam emitted from the LED lightsource 8 and entering the translucent member through the end facethereof can propagate in the member by repeated reflections, the angle θof the light beam with respect to the X-axis has to satisfy the narrowerone of the above-mentioned two conditions.

If θ_(lim) is taken as the smaller one of θ_(c) and (90-θ_(c)), thereshould be satisfied a condition −θ_(lim)<θ<θ_(lim).

In order that the light beam can enter and be reflected by thesawtooth-shaped reflecting faces 7, the angle θ of the light beam has tobe in the negative range, or a range from 0 to θ_(lim), as shown in FIG.28. If the angle α of each reflecting face 7, with respect to theX-axis, is selected as α={90+(−θ_(lim)/2)}/2, the light beam isreflected within an angular range of 90° ±(θ_(lim)/2) with respect tothe X-axis and is released to the exterior through an exit areapositioned opposite to the area 5. If the exit area and the X-axis aresubstantially parallel, the incident angle of the light beam to the exitarea does not exceed (θ_(lim)/2). Since θ_(lim) is defined as thesmaller one of θ_(c) and (90-θ_(c)), there stands a relationθ_(lim)≦θ_(c), indicating that the incident angle to the exit area issmaller than the critical angle.

Consequently, there is reduced the proportion of the light which istotally reflected on the exit area, then proceeds inversely in thetranslucent member and is released from the entrance end face thereof,and there is obtained an illumination device of a higher illuminationintensity, with a higher efficiency of utilization of the light.

Even if the above-mentioned angle α does not completely coincide withthe foregoing definition {90+(−θ_(lim)/2)}/2, a similar effect can beobtained as long as a condition: (90-θ_(c))<α<(90 +θ_(c)-θ_(lim)) issatisfied, because the incident angle of the light beam reflected by thesawtooth-shaped reflecting faces 7 and entering the exit area exceedsthe critical angle θ_(c).

For example, if the translucent member 3 is composed of acrylic resin,there is obtained a condition θ_(lim)=θ_(c)≅42°. Thus, by selecting theangle α as {90+(−42/2)}/2=34.5≅35°, it is possible to efficiently takeout the light beam, entering from the LED light source 8, from thetranslucent member 3. In terms of the angle α mentioned above, thiscorresponds to a condition 24°<α<47°.

If the diameter of the translucent member 3 is sufficiently smaller thanthe length thereof, the light propagating therein is almost uniformlydistributed within a range from +θ_(lim) to −θ_(lim). It is thereforepreferable to select the angle α as close as possible to 90+(−θlim/2)because the principal ray of the emerging light beam becomesperpendicular to the exit area.

FIGS. 29A to 29C and 30A to 30C respectively show variations of theillumination devices shown in FIGS. 20A to 20C and 21A to 21C, whereinthe area 5 is modified to the sawtooth-shaped reflecting faces 7.

Such sawtooth-shaped reflecting faces formed on the end face of theprotruding portion 35 allow not only to reduce the unevenness in theillumination intensity but also to increase the average illuminationintensity.

Embodiment 12

As explained in the foregoing, the light entering the translucent member3 may be released to the exterior upon reaching the end face thereof,and such phenomenon results in a lowered efficiency of lightutilization. Such loss is mostly represented by a proportion of thelight that has never entered the area 5 during repeated reflectionswithin the translucent member 3. Also, among the light emitted from theLED light source 8, an angular component perpendicular to the lateralfaces of the translucent member 3 or close thereto repeats thereflections between the lateral faces, as shown in FIG. 33, and does noteasily enter the area 5. It is therefore possible to further improve theillumination efficiency by causing a reflection so as to facilitate theentry of the light into the area 5 in the course of propagation withinthe translucent member 3, as will be explained in the following.

FIGS. 31A to 31C schematically show another embodiment of theillumination device of the present invention, wherein FIG. 31A is aschematic lateral view of the illumination device, illustrated togetherwith an original constituting the illuminated surface, while FIG. 31B isa schematic cross-sectional view of the translucent member 3 and thearea 5, along a plane perpendicular to that of FIG. 31A, and FIG. 31C isa schematic lateral view of the device, seen from a direction A shown inFIG. 31A. The basic configuration of the illumination device of thepresent embodiment is the same as that shown in FIGS. 17A to 17C, exceptthat a lateral face of the translucent member 3, positioned opposite tothe area 5, is made non-parallel to another lateral face at the side ofthe area 5, and that the transversal length of a face, bearing the area5 thereon, of the translucent member 3 is made shorter than that of theopposite face at the illuminated surface side. Stated differently, alateral face of the translucent member 3, positioned farther from thearea 5, is formed as an inclined face 201, spread toward the illuminatedsurface.

A part of the light emitted from the LED light source 8 repeatsreflections within the translucent member 3 as mentioned above and asillustrated in FIG. 32, but, in this embodiment, the inclined lateralface modifies the angle of reflection, thereby increasing theprobability of entry into the area 5. As a result, the efficiency ofutilization of the light emitted from the LED light source is improved,whereby the illumination intensity can be increased.

Such an inclined lateral wall is also applicable to the foregoingtranslucent members of other shapes. In any case, the presence of suchan inclined lateral face increases the probability of light entry,thereby attaining a further increase in the illumination intensity. Asexamples, FIGS. 34A to 34C show a variation, having such an inclinedlateral face 201 in the translucent member 3, in the illumination deviceshown in FIGS. 20A to 20C, and FIGS. 35A to 38C show variations, havingsimilar inclined lateral faces 201 on both lateral faces of thetranslucent member 3, in the embodiments shown in FIGS. 22A to 25C. Inthe translucent member including the extended portion, as shown in FIGS.35A to 38C, the inclined face may be formed on at least either of thelateral faces. Also, the area 5 in these cases may naturally be eitherof the diffusing type and the reflecting type explained before.

Embodiment 13

For further increasing the illumination intensity, as explained in theforegoing, it is effective to condense the light beam, emerging from thetranslucent member, with a lens. However, if such lens is incorporatedas a separate component into the illumination device, there will resultan increase in the cost, because of the high precision required foralignment of the lens, and of an increased number of assembling steps.Also, since the lens is formed as a separate component, there willresult a loss of the light, at the entry of the emerging light into thelens, by reflection on the lens surface. Although such a loss byreflection is about 4% at maximum, such a loss should naturally beprevented in order to increase the illumination intensity.

Such a reflection loss can be substantially avoided by applying anantireflective treatment to the lens surface. However, such a treatmentraises the cost, because of the steps required for such anantireflective treatment. Also, the antireflective treatment can resolvethe problem of reflection on the lens surface, but is unable to resolvethe above-mentioned problems associated with the precision of assemblingor the number of steps required therefor.

It is therefore desirable, in the formation of the translucent memberwith a plastic material such as acrylic resin or with glass, tointegrally form the lens at the same time. With either material, thetranslucent member and the lens can be integrally formed, for example,by molding.

FIGS. 39A to 39C schematically show another embodiment of theillumination device of the present invention, wherein FIG. 39A is aschematic lateral view of the device, illustrated together with anoriginal constituting the illuminated surface, FIG. 39B is a schematiccross-sectional view of the translucent member 3 and the area 5 along aplane perpendicular to that of FIG. 39A, and FIG. 39C is a schematiclateral view of the device, seen from a direction A shown in FIG. 39A.The basic structure of this embodiment is the same as that shown in FIG.17A to 17C, except that a face of the translucent member 3, opposite tothe face bearing the area 5 thereon, is formed as a convex lens 36.

With such a configuration, the light beam diffused and reflected in thearea 5 is condensed by the function of the lens portion 36. In thedevice shown in FIGS. 39A to 39C, the light diffused and reflected inthe area 5 emerges from the lens portion 36 of the translucent member 3in a state of a substantially parallel light beam, as will be explainedin the following with reference to FIG. 40.

As shown in FIG. 40, a part of the light emitted from the LED lightsource 8 enters the area 5 after at least a reflection in thetranslucent member 3. The incident light to the area 5 is diffuselyreflected therein, and a part of the light is reflected again in thetranslucent member 3, while the remaining part proceeds toward the lensportion 36, and, upon emerging therefrom, it is condensed by the lenseffect thereof and is emitted, in a state of a substantially parallellight beam, toward the illuminated surface.

Therefore, since the illuminated surface can be illuminated with asufficiently high illumination intensity even when the illuminationdevice is distanced from the surface, there can be achieved extremelyefficient illumination. Also, for the same reason, the informationprocessing apparatus employing the illumination device has a largerfreedom in designing.

Furthermore, the structure shown in FIGS. 39A to 39C can achieve moreuniform illumination, in comparison with the structure shown in FIGS.17A to 17C, because the translucent member 3 is extended laterally bythe lens portion 36.

In the present invention, the lens is not required to completelycondense (or focus) the light, which is diffused or reflected in thearea 5, onto the illuminated surface.

The above-explained translucent member 3 with lens function can not onlyachieve compactization and cost reduction, but can also provide anillumination device with more uniform illumination intensity. Suchtranslucent member 3 with lens function is not limited to the embodimentshown in FIGS. 39A to 39C, but, as illustrated in FIGS. 42A to 46C, thelens function may naturally be given to the translucent members 3 of theillumination devices shown in FIGS. 20A to 20C, 31A to 31C, 36A to 36Cand 37A to 37C.

Embodiment 14

The intensity of the indirect incident light emitted from the LED lightsource and entering the area 5 decreases as the light propagates insidethe translucent member 3 (or as the distance from the LED light sourceincreases). Also, the intensity of the direct incident light enteringthe area 5 decreases as the distance from the LED light sourceincreases. Consequently, the illumination intensity at the center of thetranslucent member tends to become lower if it is extendedlongitudinally, even when it is provided with the LED light sources atboth ends. FIG. 48A shows the relative illumination intensity along thelongitudinal direction of the translucent member 3, in the illuminationdevice shown in FIGS. 45A to 45C. As will be apparent from these charts,the distribution of the illumination intensity is significantly uniformin comparison with that in the conventional devices. Nevertheless, therelative illumination intensity is lower in the central portion in thelongitudinal direction, and it is desirable to rectify such unevenness,as will be explained in the following.

FIGS. 46A to 46C schematically illustrate another embodiment of theillumination device of the present invention, wherein FIG. 46A is aschematic lateral view of the device, illustrated together with anoriginal constituting the illuminated surface, FIG. 46B is a schematiccross-sectional view of the translucent member 3 and the area 5 along aplane perpendicular to that of FIG. 46A, and FIG. 46C is a schematiclateral view of the device, seen from a direction A shown in FIG. 46A.

As shown in these drawings, the illumination device of the presentembodiment is provided with the LED light sources 8 on both end faces ofthe translucent member 3 having a lens portion (light condensingportion). The translucent member 3 is further provided, in a positionopposite to the lens portion, with a protruding portion 35, and the area5 is formed on the end face of the protruding portion 35. The crosssection of the translucent member 3 is trapezoidal, with the shorterside closer to the area 5, bearing a convex lens portion thereon. Oneach end face, there are provided three LED light sources 8, one beingat a position corresponding to the area 5 and the remaining two beingpositioned on both sides thereof. Also, in the illustrated device, thetranslucent member 3 is made thinner in the central portion in thelongitudinal direction, than in the end portions thereof.

FIGS. 47A and 47B are respectively a schematic plan view and a schematiclateral view of the device of the present embodiment, and FIGS. 47B and47C respectively correspond to FIGS. 46A and 46C. In the presentembodiment, as shown in these drawings, the outstretched portions of thetranslucent member decrease toward the center in the longitudinaldirection, so that the cross sectional area of the member decreases fromboth ends thereof toward the center.

FIG. 48B shows the illumination intensity distribution of theabove-explained illumination device, along the longitudinal direction ofthe translucent member 3. When the translucent member 3 is constrictedin shape at the central portion as in the present embodiment, theillumination intensity in the central portion increases because thelight emitted by the LED light source 8 at an end has a higherprobability of entering the area 5 (namely becoming the indirectincident light) before reaching the other end. More specifically, thelight proceeding from an end to the other by repeated reflections iseventually reflected by the inclined face 201 to constitute the indirectincident light, due to the decrease of the out-stretched portions.Consequently, in comparison with the case without such constriction, theamount of the incident light to the area 5 increases, whereby theillumination intensity over the entire area, particularly that in anarea distant from the LED light source, can be increased.

The amount of the constriction is preferably determined in considerationof the length, thickness and cross sectional area of the translucentmember, the width of the area 5, arrangement of the LED light source,etc.

When the translucent member has the lens portion, it is desirable thatthe constriction does not affect the characteristic, for example theshape, of the lens portion, and it is also desirable to maintain aconstant distance between the area 5 and the lens face.

Also, the shape of the constriction may be linear as shown in theforegoing drawings, or may be curved or a combination of these shapes.

Furthermore, the translucent member 3 may be formed as shown in FIG. 49.The translucent member 3, excluding the lens portion, has a rectangularentrance end face for the light from the LED light source, and atrapezoidal cross section with the shorter side at the bottom, at thecentral portion in the longitudinal direction. In a position closer tothe center from the entrance end face, the cross section is rectangularwith cut-off lower comers, and the cut-off areas are progressivelyenlarged to develop into the inclined lateral faces of the trapezoidalcross section.

Such illustrated form can provide an illumination device having moreuniform illumination intensity characteristics in the longitudinaldirection.

FIGS. 50A to 50C show a variation in which the area 5 of theillumination device shown in FIGS. 46A to 46C is changed from thediffusing surface to the sawtooth-shaped reflecting faces explainedbefore. If the angle of the light condensing part, seen from the area 5,is sufficiently large (for example 60° or larger, though it depends onthe depth and shape of the protruding portion), the incident angle tothe area 5 becomes close to the perpendicular entry, but thesawtooth-shaped reflecting faces employed in the present embodimentreflect the incident light principally to the light condensing part,whereby the light emerges therefrom in a parallel or substantiallyparallel light beam. Consequently, the configuration of the presentembodiment provides an illumination device with a higher illuminationintensity which is more uniform in the longitudinal direction.

FIGS. 51A to 51C show a variation in which a cylindrical lens 9 as thelight condensing part is added to the illumination device shown in FIGS.50A to 50C. Such a configuration, being capable of further condensingthe emerging parallel light beam, can illuminate the object surface witha further increased intensity.

Embodiment 15

In the following there will be explained the method of mounting the LEDlight source. In the foregoing embodiments there have been explained thearrangements of the LED light sources, but the specific mounting methodtherefor has not been explained. In the following there will be given adetailed explanation of such a mounting method. Such a mounting methodis applicable to any of the aforementioned illumination devices, or toany variation or combination thereof.

In the mounting of the LED light source, there are required the mountingprecisely at the designed position, a simple mounting process includingthe maintenance of precision, and the possibility of introduction of thelight from the LED light source into the translucent member with minimumloss. The mounting method for the LED light source has no particularlimitation, as long as these requirements are met.

A simplest example of the mounting method is to adhere the LED chip ontothe end face of the translucent member. However, such an adhesion methoddoes not allow easy replacement of the LED light source, and may lead tocertain drawbacks, such as peeling of adhesive or breakage of the LEDdue to the expansion and contraction resulting from variations intemperature and humidity, particularly when the translucent member iscomposed of a resinous material such as acrylic resin.

Also, if the LED light source is positioned separate from thetranslucent member, there may result a light loss due to a variation inthe distance between the LED light source and the end face of thetranslucent member, resulting from expansion and contraction thereof.

FIG. 52 shows a mounting method capable of avoiding these drawbacks.

In this embodiment, as shown in FIG. 52, the translucent member 3 has aprotruding portion 3 a on the end face thereof, and the LED light source8 is provided with a reflecting frame 83 extended so as to fit on theprotruding portion 3 a.

Such a structure can avoid the light leakage to the exterior due to thepresence of the reflecting frame 83, despite the eventual presence of agap between the external surface of transparent sealing resin 84 and theentrance end face 4 of the translucent member 3. Also, since a part ofthe light reflected by the reflecting frame 83 enters the translucentmember 3 through the entrance end face 4, the efficiency of utilizingthe light, emitted from the LED chip 81, can be improved. The reflectingframe 83 may be adhered to the protruding portion 3 a of the translucentmember 3, but it is preferably fitted merely on the protruding portion,in order to relax the stress resulting from the expansion or contractionof the translucent member 3 and the reflecting frame 83.

Also, the precision of positioning of the LED light source 8 can beimproved by fitting the light source 8 onto the protruding portion 3 aformed on the translucent member 3, and the mounting process can besimplified if the mount is conducted by mere fitting only.

FIG. 53 shows a variation of the mounting method for the LED lightsource shown in FIG. 52. In this variation, the LED chip is surfacemounted on a mounting board 11, and is surrounded by a reflecting frame10, which is made of white resin or a metal integrated with the board 11and is fitted on the protruding portion 3 a.

Such a configuration allows one to obtain illuminating characteristicsmatching the requested performance in an easier manner, since theprotruding portion 3 a can be formed with a desired shape and size andthe LED light source can be mounted on such a protruding portion.

An additional reflecting portion may be formed in at least a part of thearea, other than the mounting area for the LED light source. Thepresence of such reflecting portion causes the light, returning from theother end face of the translucent member, to continue the internalreflections without being released from the entrance end face, therebyimproving the efficiency of light utilization.

The presence of the above-mentioned protruding portion 3 a is notessential, but is preferable in consideration of the aforementionedimprovement in the positioning accuracy. The protruding portion 3 a canbe molded simultaneously with the formation of the translucent member 3,but it may also be formed, if necessary, by cutting and/or grinding.

The LED light source may also be mounted by fitting into a recess formedon the entrance end face of the translucent member. Such a mountingmethod causes a loss in a part of the light emitted from the LED chip,but is effective in the positioning precision and in a smallerprotruding distance in the mounting portion.

FIG. 54 is a schematic perspective view of an example of thephotoelectric converting device, utilizing the illumination device ofthe present invention shown in FIG. 53 and constituting an image readingdevice. There are shown a sensor substrate 14, a protecting glass 15,and a casing 16 of the photoelectric converting device. On the sensorsubstrate 14, there is provided a one-dimensional array (or pluralarrays) of a plurality of photoelectric converting elements, which areformed utilizing a thin semiconductor layer for example of amorphoussilicon or polysilicon. The protective glass 15 is provided on theplural photoelectric converting elements (not illustrated), forprotecting the elements from eventual breakage caused by the contactwith the moving original. The casing 16 is provided therein with a spacefor fitting with the illumination device and the cylindrical lens 9,which are set in a predetermined position by insertion from an end faceof the casing 16. The LED light sources 8 are mounted on a mountingboard 11 and mounted on the protruding portion 3 a of the translucentmember 3 by fitting the reflecting frame 10 thereon, and the mountingboard 11 is fixed by a screw 162 fitted into a threaded hole 161 formedon the casing.

The translucent member 3 is provided with mounting portions 37, engagingwith the casing 16. Naturally, the mounting portions 37 are notessential, nor are they limited to the illustrated shape. Such mountingportions 37 may naturally be provided also in the translucent members 3in the foregoing embodiments 1 to 14

Embodiment 16

In the following, there will be explained application of theillumination device of the present invention to an informationprocessing apparatus.

FIG. 55 illustrates an example of the information processing apparatus(for example, a facsimile apparatus) utilizing the photoelectricconverting device of the present invention.

There are shown a feed roller 102 for feeding an original 17 to areading position; a separating member 104 for securely separating theoriginals P one by one; and a transport roller 18 provided at the imagereading position of a photoelectric converting device 100, for definingthe image reading plane of the original 17 and also serving to transportthe original 17.

A recording medium W, in the form of rolled paper, is subjected toformation of an image read by the photoelectric converting device 100,or, in the case of a facsimile, an image transmitted from the outside. Arecording head 110, for the image formation, can be of various typessuch as a thermal head or an ink jet recording head. Also, the recordinghead can be of serial type or of line type. A platen roller 112 isprovided for transporting the recording medium W to the recordingposition by the recording head 110 and for defining the recording planeof the recording medium.

An operation panel 120 is provided with switches for entering commandsfor operations, and with a display unit for displaying messages and astatus of the apparatus.

There are further provided a system control board 130, provided thereonwith a control unit for controlling various units of the apparatus, adriving circuit for the photoelectric converting elements, a processingunit for the image information, a transmission-reception unit, etc., anda power source 140 for the apparatus.

FIGS. 56 and 57 are schematic magnified views of the photoelectricconverting device, employable in the information processing apparatusshown in FIG. 55. FIG. 56 shows the case of a contact sensor, utilizingthe photoelectric converting device (image reading device) shown in FIG.54. FIG. 57 shows the case of a system employing an imaging opticalsystem 19, wherein the original 17 is illuminated by the light emittedby illumination means of the embodiment 14 shown in FIGS. 46A to 46C,and the reflected light, corresponding to the image information, isfocused on the photoelectric converting device 20 through the imagingoptical system 19.

It is also possible, as shown in FIG. 58, to form an imaging opticalsystem 25 at the original side, and to read the image by focusing,through a protective layer (protective glass) 23, on a photoelectricconverting device 22 formed on a sensor substrate 21, utilizing a thinsemiconductor layer.

In both cases, the original surface was illuminated with extremelyuniform distribution of illumination intensity, so that the image couldbe read in an extremely excellent state.

Also, other illumination devices explained in the foregoing embodiments1 to 13 enable much superior image reading, in comparison with the caseemploying the conventional illumination devices.

The illumination device of the present invention, being capable ofproviding a sufficiently high light amount, is also suitable for colorimage reading. Also, for modifying the color temperature or the hue ofthe illuminating light, a filter may be provided between the LED lightsource and the end face of the translucent member 3, or the translucentmember itself may be dyed. In the case of such a dyeing, the entranceend face is preferably dyed, but, if surficial dyeing is enough for thepurpose, the light exit face of the translucent member is preferablydyed. This is because, if the entire translucent member is dyed orcolored, the light is attenuated significantly in the course of internalreflections, whereby the light intensity becomes lower in the centralportion or in a position distant from the LED light source.

For image output applicable to the information processing apparatusshown in FIG. 55, there can be considered, as explained above, thethermal transfer recording method or thermal recording method utilizingthe thermal head, and the ink jet recording method utilizing the ink jetrecording head.

In the following, there will be explained an embodiment of theinformation processing apparatus, employing such a recording head as theoutput means. The following explanation will be limited to the outputpart only.

Among various ink jet recording methods, the present invention bringsabout a particular effect when applied to a recording head of a systemutilizing thermal energy for ink discharge, because the entireinformation processing apparatus can fully enjoy the effect ofcompactization of the illumination device, as the recording head itselfcan be made compact.

The principle and representative configuration of the system aredisclosed, for example, in U.S. Pat. Nos. 4,723,129 and 4,740,796. Thissystem is applicable to so-called on-demand recording or continuousrecording, but is particularly effective in the on-demand recordingbecause the entire apparatus can be compactized.

In brief, in this system, an electrothermal converting member positionedcorresponding to a liquid channel or a sheet containing liquid thereinis given at least a drive signal, corresponding to the recordinginformation and capable of causing a rapid temperature increaseexceeding nucleate boiling, to generate thermal energy in theelectrothermal converting member, thereby inducing film boiling on aheat action surface of the recording head and forming a bubble in theink in one-to-one correspondence to the recording signal. The ink isdischarged from a discharge opening by the growth and contraction of thebubble, thereby forming at least an ink droplet. The signal ispreferably formed as a pulse, as it realizes instantaneous growth andcontraction of the bubble, thereby attaining highly responsive dischargeof the ink.

Such a pulse-shaped drive signal is preferably as disclosed in U.S. Pat.Nos. 4,463,359 and 4,345,262. Also, the conditions described in U.S.Pat. No. 4,313,124 relative to the temperature increase rate of the heataction surface allows one to obtain a further improved recording.

The configuration of the recording head is given by the combinations ofthe ink discharge openings, liquid channels and electrothermal converterelements with linear or rectangular liquid channels, as disclosed in theabove-mentioned patents, but a configuration disclosed in U.S. Pat. No.4,558,333 in which the heat action part is positioned in a flexed area,and a configuration disclosed in U.S. Pat. No. 4,459,600 also belong tothe present invention.

Furthermore, the present invention is effective in a structure disclosedin Japanese Patent Laid-open Application No. 59-123670, having a slitcommon to plural electrothermal converter elements as a dischargeopening therefor, or in a structure disclosed in Japanese PatentLaid-open Application No. 59-138461, having an aperture for absorbingthe pressure wave of thermal energy, in correspondence with eachdischarge opening.

A full-line type recording head, capable of simultaneously recordingover the entire width of the recording sheet, may be obtained by pluralrecording heads combined so as to provide the required length asdisclosed in the above-mentioned patents, or may be constructed as asingle integrated recording head.

Furthermore, there may be employed a recording head of aninterchangeable chip type, which can receive an ink supply from the mainapparatus and can be electrically connected therewith upon mounting onthe main apparatus, or a recording head of cartridge type in which anink cartridge is integrally constructed with the recording head.

Also, the information processing apparatus of the present invention ispreferably provided with the discharge recovery means and otherauxiliary means for the recording head, in order to realize a furtheradvanced maintenance-free system.

Examples of such means for the recording head include capping means,cleaning means, pressurizing or suction means, heating means composedfor example of an electrothermal converter element for heating therecording head, and means for effecting an idle ink dischargeindependent from the recording operation, all of which are effective forachieving stable recording operation.

Furthermore, the recording mode is not limited to recording of a singlemain color, such as black, but also covers recording of plural colors ora full-color image, by means either of an integrally constructedrecording head or of a combination of plural recording heads.

In the foregoing explanation, the ink is assumed to be liquid, but theremay also be employed ink which is solid below room temperature butsoftens at room temperature. In the above-explained ink jet recordingsystem, the ink itself is usually temperature controlled within a rangeof 30° C.-70° C. for maintaining the ink viscosity within a stabledischarge range, so that the ink needs to be liquid only when therecording signal is given. In addition, there may also be employed inkwhich is intentionally changed from solid to liquid by heating withthermal energy.

In the following, there will be given a brief explanation of an ink jetrecording head, utilized in such an ink discharge recording systemutilizing thermal energy.

FIG. 59 is a schematic view of such an ink jet recording head, composedof electrothermal converter elements 1103, electrodes 1104, liquidchannels 1105 and a ceiling plate 1106, formed on a substrate 1102through a semiconductor process involving the steps of etching,evaporation, sputtering, etc. The recording ink 1112 is supplied from anunrepresented ink reservoir to a common ink chamber 1108 of therecording head 1101 through a supply pipe 1107, provided with aconnector 1109 therefor.

The ink 1112 in the common ink chamber 1108 is supplied into the liquidchannel 1110 by capillary action, and is stably held therein, by forminga meniscus at the discharge opening (orifice) at the end thereof.Electric power supply to the electrothermal converter element 1103rapidly heats the liquid thereon, thus forming a bubble in the liquidchamber, and the liquid is discharged from the opening 1111 by theexpansion and contraction of the bubble, thereby forming a liquiddroplet.

The above-explained configuration allows to arrange the dischargeopenings with a high density such as 16 nozzle/mm or even higher,thereby obtaining an ink jet head with 128 or 256 discharge openings, oreven a full-line ink jet recording head having an array of the dischargeopenings over the entire recording width.

FIG. 60 is a schematic perspective view of the external structure of anoutput unit utilizing the ink jet recording method.

In FIG. 60 there are shown an ink jet recording head 1801 fordischarging ink according to the recording signals, thereby recording adesired image; and a carriage 1802 for moving the recording head 1801 inthe recording (main scanning) direction. The carriage 1802 is slidablysupported by guide shafts 1803, 1804, and reciprocates in the mainscanning direction by means of a timing belt 1808, which is supported bypulleys 1806, 1807 and driven by a carriage motor 1805 through thepulley 1807.

A recording sheet 1809 is guided by a paper pan 1810, and is pressed, bypinch rollers, to an unrepresented transport roller for transporting thesheet.

The sheet transportation is achieved by a feeding motor 1816. Thetransported recording sheet 1809 is given a tension by a dischargeroller 1813 and a grooved roller 1814, and is transported in closecontact with a heater 1811, by means of an elastic pressure plate 1812.Thus the recording sheet 1809, bearing thereon the ink, discharged fromthe recording head 1801 and deposited on the sheet, is heated by theheater 1811, whereby the deposited ink is dried and fixed to therecording sheet 1809.

A recovery unit 1815 is provided for maintaining the proper inkdischarge state of the recording head 1801, by removing the dusts andhighly viscous ink, deposited on the discharge openings (notillustrated) of the recording head 1801.

A cap member 1818 a, constituting a part of the recovery unit 1815, isprovided to cap the discharge openings of the recording head 1801,thereby preventing the clogging of the openings. Inside the cap 1818 a,there is preferably provided an ink absorbent member 1818.

At a side of the recovery unit 1815, closer to the recording area, thereis provided a blade 1817 for coming into contact with a face, having thedischarge openings, of the recording head 1801, thereby eliminating thedust and ink sticking to the face.

In the present invention, as shown in a block diagram in FIG. 61, theoriginal transported by original transmission means 2007 to the imagereading part of an image reading device 2000 is read by photoelectricconverter elements 2001 thereof, then thus obtained electrical signalsbearing image information are converted by image processing means (notshown) into electrical signals for recording, and the recordingoperation is conducted by a controller such as a CPU 2000 controllingthe carriage motor 2003, recording head 2004, sheet feeding motor 2005,recovery unit 2006, etc.

The electrical signals bearing image information may be transmittedthrough communication means 2008 to another image processing apparatusfor image output therein, or may be received from another informationprocessing apparatus through the communication means 2008 and recordedby the above-mentioned recording head 2004.

FIG. 62 schematically shows the output unit provided with a recordinghead 1932 of full-line type.

A conveyor belt 1965 transports an unrepresented recording medium, bythe rotation of a transport roller 1932. The bottom face 1931 of therecording head 1932 is provided with a plurality of discharge openings,corresponding to the recording area of the recording medium.

Also, in this case the recording operation can be conducted in a similarmanner as in the recording head of serial type explained above.

Naturally, the output units explained above are given as examples, andthere can be conceived various modifications.

However, the above-explained ink discharge system utilizing thermalenergy, being capable not only of compactization but also of more highlyprecise recording, can exhibit the effect of the present invention moreconspicuously, and can therefore provide an information processingapparatus excellent in overall performance.

As explained in detail in the foregoing, the present invention canprovide a compact illumination device capable of uniform illuminationwith a high intensity.

Also, the present invention can provide an illumination device which issimple in structure and can simplify also the manufacturing process.

Furthermore, the present invention can provide a photoelectricconverting device and an information processing apparatus capable ofstable image reading.

Furthermore, the present invention can provide a secure mounting methodfor the light source, which is simplified in the mounting steps.

Furthermore, the present invention can realize a linear light sourcewith reduced unevenness in the amount of illuminating light on theilluminated surface, thereby achieving improved tonal rendition withoutincreasing the burden of image processing.

The present invention is subject to various modifications within thescope and spirit of the appended claims. Also, the embodiments explainedbefore may naturally be combined in suitable manner.

1. An information processing apparatus comprising: an illuminationdevice provided with a longitudinal light guide, for guiding lightintroduced from a light source and for emitting the light along alongitudinal side thereof, having a longitudinal reflection memberarranged along said light guide for reflecting the light from said lightsource; a photoelectric converting device having a plurality ofphotoelectric conversion elements for reading an image illuminated bysaid illumination device and for outputting an image signal; and aprocessor for processing the image signal output from said photoelectricconverting device.
 2. An information processing apparatus comprising: anillumination device provided with a longitudinal light guide, forguiding light introduced from a plurality of light sources and foremitting the light along a longitudinal side thereof, having alongitudinal reflection member arranged along said light guide forreflecting the light from said plurality of light sources; aphotoelectric converting device having a plurality of photoelectricconversion elements for reading an image illuminated by saidillumination device and for outputting an image signal; and a processorfor processing the image signal output from said photoelectricconverting device.